Final answer:
Max Vandenburg's voice is compared to friction, indicating a rough yet potentially soothing quality, similar to a stone rubbing against a rock. Therefore, the correct option is C.
Step-by-step explanation:
In the provided example, a simile is used to compare Max Vandenburg's voice to the sensation of friction, similar to that of a stone gently rubbing against a large rock. Therefore, the elements being compared are (c) Max Vandenburg's voice and friction. This comparison illustrates how Max's voice contains a certain roughness or grating quality that could be soothing or persistent, much like the continuous motion of a stone being rubbed against a surface.